[wasm-split] Run RemoveUnusedElements on secondary modules (#6945)

Rather than analyze what module elements from the primary module a
secondary module will need, the splitting logic conservatively imports
all module elements from the primary module into the secondary module.
Run RemoveUnusedElements on the secondary module to remove any of these
imports that happen to be unnecessary. Leave a TODO mentioning the
possibility of being more selective about which module elements get
exported to reduce code size in the primary module, too.

1 files changed, 6 insertions, 5 deletions

diff --git a/src/tools/wasm-split/wasm-split.cpp b/src/tools/wasm-split/wasm-split.cpp
index ea1734b6b..2b66d1164 100644
--- a/src/tools/wasm-split/wasm-split.cpp
+++ b/src/tools/wasm-split/wasm-split.cpp
@@ -69,11 +69,15 @@ uint64_t hashFile(const std::string& filename) {
   return uint64_t(digest);
 }
 
-void adjustTableSize(Module& wasm, int initialSize) {
+void adjustTableSize(Module& wasm, int initialSize, bool secondary = false) {
   if (initialSize < 0) {
     return;
   }
   if (wasm.tables.empty()) {
+    if (secondary) {
+      // It's not a problem if the table is not used in the secondary module.
+      return;
+    }
     Fatal() << "--initial-table used but there is no table";
   }
 
@@ -336,7 +340,7 @@ void splitModule(const WasmSplitOptions& options) {
   auto& secondary = splitResults.secondary;
 
   adjustTableSize(wasm, options.initialTableSize);
-  adjustTableSize(*secondary, options.initialTableSize);
+  adjustTableSize(*secondary, options.initialTableSize, /*secondary=*/true);
 
   if (options.symbolMap) {
     writeSymbolMap(wasm, options.primaryOutput + ".symbols");
@@ -435,9 +439,6 @@ void multiSplitModule(const WasmSplitOptions& options) {
     // TODO: symbolMap, placeholderMap, emitModuleNames
     // TODO: Support --emit-text and use .wast in that case.
     auto moduleName = options.outPrefix + mod + ".wasm";
-    PassRunner runner(&*splitResults.secondary);
-    runner.add("remove-unused-module-elements");
-    runner.run();
     writeModule(*splitResults.secondary, moduleName, options);
   }
   writeModule(wasm, options.output, options);